The present invention relates to a crank pin phase indexing apparatus and an indexing method, which are employed in crank pin grinding machines and the like.
Japanese Unexamined Patent Publication No. Hei 3-19757 discloses a known crank pin phase indexing apparatus having a pair of main spindles. In this prior art indexing apparatus, a chuck body is attached to the nose of each main spindle, and the chuck supports a phasing rotary shaft rotatable about an axis offset from the axis of the main spindle. A phase indexing shaft is supported in the main spindle along the center thereof to rotate relative to the main spindle on the same axis, and the distal end of the phase indexing shaft is connected to the phasing rotary shaft via a first coupling.
A second coupling is located between the main spindle and the phase indexing shaft and releasably connects them. A differential gear mechanism is located between a drive motor and the main spindle and phase indexing shaft, and the main spindle and the phase indexing shaft are rotated, with the rotation of the drive motor, integrally or relative to each other via the differential gear mechanism. Further, a braking mechanism is connectable either to the main spindle or the phase indexing shaft.
Indexing of a work crankshaft with respect to the axis of the main spindle is carried out after the second coupling is disengaged from the main spindle and after the main spindle is engaged with the braking mechanism. Since the main spindle is locked against rotation in this state, if the drive motor is driven, the phase indexing shaft is rotated relative to the main spindle via the differential gear mechanism. This rotation of the phase indexing shaft is transmitted to the phasing rotary shaft to achieve indexing of the workpiece supported by the chuck body at a predetermined phase with respect to the center of the workpiece.
When the main spindle is to be rotated, the second coupling is engaged with the main spindle and the braking mechanism is disengaged from the main spindle. Since the main spindle and the phase indexing shaft are connected to each other integrally in this state, the main spindle and the phase indexing shaft are rotated integrally via the differential gear mechanism when the drive motor is driven. Thus, the workpiece supported by the chuck bodies is rotated on the axis of the main spindle with a predetermined indexed phase. The workpiece chucked by the chuck body is rotated and machined.
However, in this prior art crank pin phase indexing apparatus, a differential gear mechanism is located between the drive motor and the main spindle and phase indexing shaft, and the main spindle and the phase indexing shaft are rotated via this differential gear mechanism integrally or relative to each other for machining or indexing. Accordingly, a differential gear mechanism having a multiplicity of gears must be incorporated into the apparatus, which complicates the apparatus, degrades the working environment with gear beating noise and lowers the accuracy of the apparatus due to abrasion of the gears.